PR middle-end/11968

	* expr.c (expand_expr <MULT_EXPR>): Remove inappropriate and
	confusing comment; distributivity isn't handled in expand_expr.
	* fold-const.c (extract_muldiv_1 <PLUS_EXPR>):  Allow overflow
	in distributivity, if wrap-around semantics are specified with
	-fwrapv.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@73166 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a4ca9c7..7a21708 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2003-10-31  Roger Sayle  <roger@eyesopen.com>
+
+       PR middle-end/11968
+       * expr.c (expand_expr <MULT_EXPR>): Remove inappropriate and
+       confusing comment; distributivity isn't handled in expand_expr.
+       * fold-const.c (extract_muldiv_1 <PLUS_EXPR>):  Allow overflow
+       in distributivity, if wrap-around semantics are specified with
+       -fwrapv.
+
 2003-11-01  Alan Modra  <amodra@bigpond.net.au>
 
        PR 12315

diff --git a/gcc/expr.c b/gcc/expr.c
index cd37495..347edb3 100644 (file)
--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -7854,16 +7854,6 @@ expand_expr (tree exp, rtx target, enum machine_mode tmode,
          op0 = expand_expr (TREE_OPERAND (exp, 0), subtarget, VOIDmode,
                             EXPAND_SUM);
 
-         /* If we knew for certain that this is arithmetic for an array
-            reference, and we knew the bounds of the array, then we could
-            apply the distributive law across (PLUS X C) for constant C.
-            Without such knowledge, we risk overflowing the computation
-            when both X and C are large, but X+C isn't.  */
-         /* ??? Could perhaps special-case EXP being unsigned and C being
-            positive.  In that case we are certain that X+C is no smaller
-            than X and so the transformed expression will overflow iff the
-            original would have.  */
-
          if (GET_CODE (op0) != REG)
            op0 = force_operand (op0, NULL_RTX);
          if (GET_CODE (op0) != REG)

diff --git a/gcc/fold-const.c b/gcc/fold-const.c
index 85909a3..3787915 100644 (file)
--- a/gcc/fold-const.c
+++ b/gcc/fold-const.c
@@ -4433,8 +4433,11 @@ extract_muldiv_1 (tree t, tree c, enum tree_code code, tree wide_type)
       if (code == MULT_EXPR
          || integer_zerop (const_binop (TRUNC_MOD_EXPR, op1, c, 0)))
        {
-         op1 = const_binop (code, convert (ctype, op1), convert (ctype, c), 0);
-         if (op1 == 0 || TREE_OVERFLOW (op1))
+         op1 = const_binop (code, convert (ctype, op1),
+                            convert (ctype, c), 0);
+         /* We allow the constant to overflow with wrapping semantics.  */
+         if (op1 == 0
+             || (TREE_OVERFLOW (op1) && ! flag_wrapv))
            break;
        }
       else